(a) Technical Field
The present disclosure relates to a driving device for a display device and an image signal compensating method therefor.
(b) Discussion of Related Art
As one of the current widely-used flat panel display devices, a liquid crystal display device includes two display panels on which field generating electrodes, such as a pixel electrode, and a common electrode, are disposed and a liquid crystal layer interposed therebetween. When voltages are applied to the field generating electrodes, an electric field is generated in the liquid crystal layer to determine alignment of the liquid crystal molecules of the liquid crystal layer and to control polarization of incident light, so that an image can be displayed.
The liquid crystal display includes switching elements connected to the pixel electrodes and a plurality of signal lines such as gate and data lines for controlling the switching elements to apply voltages to the pixel electrodes.
Such a liquid crystal display has been widely used as a display screen for a television set or the like, as well as a display device for a computer. Therefore, there is a need to display motion pictures on the liquid crystal, display. Since a response speed of the liquid crystal molecules of the liquid crystal display is slow, however, it is difficult to display the motion picture properly.
More specifically, since the response speed of the liquid crystal molecule is slow, a finite amount of time is spent until a voltage charged in a liquid crystal capacitor approaches a target voltage, that is, a voltage by which the desired luminance can be obtained. The time varies with a difference between the target voltage and a voltage previously charged in the liquid crystal capacitor. For example, when the target voltage is quite different from the previously charged voltage, the target voltage may not be obtained by applying only the previous voltage during a time that the switching element is turned on.
On the other hand, in such a liquid crystal display, particularly, a liquid crystal display using a vertical electric field, optical phase retardation of the liquid crystal molecules varies with a viewing angle, so that a front transmittance characteristic is different from a side transmittance characteristic. As a result, front visibility is different from side visibility.
As a result of an experiment for measuring transmittance of a liquid crystal display according to gray values, in a low gray value, the transmittance increases in a side portion. On the contrary, in a high gray value, the transmittance decreases in the side portion. In this manner, due to difference in transmittance according to the viewing angle, the difference in transmittance between the gray values decreases in the side portion, so that side visibility deteriorates.
As a method of preventing deterioration in the side visibility, there has been proposed a method of dividing one pixel into two subpixels and applying a normal voltage to the one subpixel and a higher or lower voltage to the other subpixel, so as to charge the liquid crystal capacitor with different voltages, so that the visibility can be improved.
In the method of dividing one subpixel into two subpixels, however, since it is difficult to apply accurate voltages suitable for the gray values, there is a limitation on improving the visibility.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.